Anesthesiology
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The wakeful brain can easily access and coordinate a large repertoire of different states-dynamics suggestive of "criticality." Anesthesia causes loss of criticality at the level of electroencephalogram waveforms, but the criticality of brain network connectivity is less well studied. The authors hypothesized that propofol anesthesia is associated with abrupt and divergent changes in brain network connectivity for different frequencies and time scales-characteristic of a phase transition, a signature of loss of criticality. ⋯ Around loss of behavioral responsiveness, a small increase in propofol concentrations caused a collapse of long time scale power envelope connectivity and an increase in 10 Hz phase-based connectivity-suggestive of a brain network phase transition.